In the early 1930's, Zintl and coworkers showed that the electrolysis of certain main group, main group alloy, and intermatallic phases could produce metal polyanions in the catholyte. Through the potentiometric titrations of liquid ammonia solutions of these salt-like intermetallic compounds, and exhaustive extractions of alkali metal alloys of the heavier group 14 and 15 elements, they were able to deduce the existence of Sn.sub.9.sup.4-, Pb.sub.9.sup.4-, Pb.sub.7.sup.4-, As.sub.3.sup.3- As.sub.7.sup.3-, Sb.sub.7.sup.3-, Sb.sub.3.sup.3-, Bi.sub.7.sup.3-, Bi.sub.5.sup.3- and Bi.sub.3.sup.3- but apparently did not isolate crystalline derivatives of these species to confirm their findings. These metal polyanions, which have come to be known as Zintl phases, are unique in that they have no exopolyhedral ligands at the vertices and so can easily form metal--metal bonds, which make them ideal precursors for the preparation of conducting and semiconducting films and solids by topochemical or bulk oxidations, respectively. Such films might have a variety of uses, including use as coatings. The novel polyanions of the present invention should have the same uses.
Additionally, after an initial report in 1970 on the ethylenediamine extraction and isolation of Sn.sub.9.sup.4- from Na.sub.4, Sn.sub.9, a variety of homopolyatomic and heteropolyatomic anions have been isolated via the solvent extraction of Zintl phases including Se.sub.6.sup.2-, Te.sub.4.sup.2-, Tl.sub.2 Te.sub.2.sup.2-, TlSn.sub.8.sup.-3, As.sub.2 Se.sub.6.sup.3-, SnTe.sub.4.sup.4-, Sn.sub.2 Te.sub.6.sup.4-, HgTe.sub.12.sup.4-, As.sub.10 Te.sub.3.sup.2- among others. These are seen to include Group 16 elements in addition to Group 14 and 15 elements.
The term Zintl phase has often been used to define an intermetallic compound comprising one element of the alkali and/or alkaline earth metals and one or more elements from the main group elements. It will be used herein to define a compound that has been prepared electrolytically and that comprises an organic cation and a polyanion involving a metal-to-metal bond of atoms of the same or different metals of the main group or transition group of metals. Moreover, as used herein gallium, germanium, aresenic, selenium, indium, tin, antimony, tellurium, thallium lead and polonium are considered to be the main group of metals while titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum and gold are considered to be the transiton group metals. Such a polyanion will also be referred to as a Zintl anion.